Land clearing triggers hotter droughts: new research finding

26 October 2007

A University of Queensland scientist has led groundbreaking research which shows that clearing of native vegetation has made recent Australian droughts hotter.

Dr Clive McAlpine of UQ’s Centre for Remote Sensing and Spatial Information Science and Mr Jozef Syktus, principal scientist in the Queensland Natural Resources and Water Department (DNRW), headed a study which will be published later this year in Geophysical Research Letters, the journal of the American Geophysical Union.

In an Australian first, they applied the CSIRO Mark 3 climate model, satellite data and the DNRW supercomputer, and showed that 150 years of land clearing added significantly to the warming and drying of eastern Australia.

“Our work shows that the 2002-03 El Nino drought in eastern Australia was on average two degrees Centigrade hotter because of vegetation clearing,” Dr McAlpine said.

“Based on this research, it would be fair to say that the current drought has been made worse by past clearing of native vegetation.

“Our findings highlight that it is too simplistic to attribute climate change purely to greenhouse gases.

“Protection and restoration of Australia's native vegetation needs to be a critical consideration in mitigating climate change.”

Co-authors are Dr Hamish McGowan, Associate Professor Stuart Phinn and Dr Ravinesh Deo – all of UQ – Dr Peter Lawrence of the University of Colorado and Dr Ian Watterson of CSIRO.

The researchers found that mean summer rainfall decreased by between four percent and 12 percent in eastern Australia, and by four percent and eight percent in southwest Western Australia. These were the regions of most extensive historical clearing.

“Consistent with actual climate trends, eastern Australia was between 0.4 degrees Centigrade and two degrees Centigrade warmer, and southwest Western Australia was between 0.4 degrees and 0.8 degrees warmer.

“Native vegetation moderates climate fluctuations, and this has important, largely unrecognised consequences for agriculture and stressed land and water resources,” Dr McAlpine said.

Australian native vegetation holds more moisture that subsequently evaporates and recycles back as rainfall. It also reflects into space less shortwave solar radiation than broadacre crops and improved pastures, and this process keeps the surface temperature cooler and aids cloud formation.

The project, Modeling Impacts of Vegetation Cover Change on Regional Climate, was funded by Land and Water Australia Research and Development Corporation (Canberra) as part of their Innovation Research Program.